Fundamental Concepts of Biology: From Cells to Ecosystems
Characteristics of Living Organisms
- Sensitivity
- Organisms respond to diverse stimuli.
- Adaptation
- All living organisms exhibit a “fit” to their environment.
- Metabolism
- This refers to the chemical reactions that occur within living organisms to maintain life.
- Homeostasis
- The ability of an organism to maintain constant internal conditions.
- Organization / Order
- Organisms are highly organized structures. The cell is the basic unit of life.
Levels of Biological Organization
- Population
- A group of organisms of the
Milestones in Genetics: History, Concepts, and Disorders
Key Historical Discoveries in Genetics (8000 B.C. – 1962)
| Year | Discovery / Event | Scientist(s) Involved |
|---|---|---|
| 8000–1000 B.C. | Humans knew sexual reproduction caused variation (used in selective breeding). | Ancient humans |
| 1856–1863 | Hybridization experiments on garden peas (basis of inheritance laws). | Gregor Johann Mendel |
| 1865 | Publication of Mendel’s work, “Experiments on Plant Hybridization”. | Mendel |
| 1866 | First description of Down Syndrome. | Langdon Down |
| 1891 | Discovery of the X-body (X chromosome) during spermatogenesis |
Viral Immunity and Pathogenesis: Host Defense Mechanisms and Infection Outcomes
Host Defense Mechanisms Against Viruses
Innate, Intrinsic, and Adaptive Immunity
- Innate Immunity: Non-specific, immediate response. Uses Pattern Recognition Receptors (PRRs) to detect Pathogen-Associated Molecular Patterns (PAMPs).
- Intrinsic Immunity: Always present in cells (pre-existing defenses).
- Examples: TRIM proteins, MxA, Tetherin, autophagy, apoptosis.
- Adaptive Immunity: Specific, develops after infection.
- Two arms: T cells (cell-mediated) and B cells (antibody-mediated/humoral).
Pathogen-Associated
Read MoreComparative Adaptations for Respiratory Gas Exchange
The Process of Gas Exchange
Gas exchange is the vital physiological process by which oxygen ($ ext{O}_2$) from the environment is taken into the body and carbon dioxide ($ ext{CO}_2$), a waste product of cellular respiration, is removed. In animals, this process typically occurs across specialized respiratory surfaces, such as:
- Lungs (mammals, birds, reptiles)
- Gills (fish, some amphibians)
- Skin (some amphibians, invertebrates)
Oxygen diffuses across thin, moist membranes into the bloodstream or directly
Read MoreMolecular Genetics: Key Concepts and Mutation Effects
Molecular Genetics Fundamentals
Cellular Transformation and Key Enzymes
Transformation studies demonstrate the ability to transition from non-disease-causing to disease-causing states, often involving the uptake of genetic material.
Enzyme Definitions
- Enzyme that degrades DNA: DNase
- Enzyme that degrades protein: Protease
- Enzyme that degrades RNA: RNase
Cell Types and Ploidy
- Somatic Cells: Non-reproductive cells (diploid).
- Gametes: Reproductive cells (haploid), containing half the amount of DNA as somatic
Plant Nutrition Mechanisms: Photosynthesis and Nutrient Uptake
Core Functions of Organic Molecules
Plants require organic molecules for two primary functions:
- To obtain the energy required for vital functions.
- To increase size, develop, and form new organs.
Autotrophic Organisms
In addition to plants, other organisms are autotrophs, including many protists, Monera, and algae.
Phases of Plant Nutrition
Plant nutrition involves two main parts:
- Organic Synthesis (Photosynthesis): The process by which light energy is transformed into chemical energy, converting inorganic